Catching a Milky Way open cluster in its last breath

TL;DR

This paper presents the first observational evidence of an open cluster, ASCC 92, in a transitional dynamical state with stars in the process of escaping, supporting theoretical models of cluster dissolution.

Contribution

It provides the first empirical detection of potential escapers within an open cluster, confirming theoretical predictions about cluster dissolution stages.

Findings

ASCC 92 has lost nearly 90% of its initial mass.

Stars in ASCC 92 exhibit hot kinematics indicative of escape.

The cluster is moving toward regions with higher interstellar absorption.

Abstract

Theoretical models have suggested peculiar velocity dispersion profiles of star clusters facing dissolution. They predicted that, besides bound stars that still belong to the star cluster, and unbound ones already stripped off, there is an intermediate population of stars that having acquired the enough energy to escape the cluster are still within the cluster Jacobi radius. Both, potential escapers and unbound stars, show hot kinematics, not observed along tidal tails of star clusters. We report on the first evidence of an open cluster with stars crossing such a transitional scenario, namely: ASCC 92. The open cluster gathers nearly 10 percent of its initial total mass, and is moving toward Galactic regions affected by higher interstellar absorption. Precisely, the obscured appearance of the cluster could have hampered disentangling its true internal dynamical evolutionary stage, previously.